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Help with xover and port ideas for MTM project

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  • Help with xover and port ideas for MTM project

    I have a pair of powered monitors I bought from CSS a few years ago and I want to convert them to passive to be powered by my 2-channel Hypex UCD180 amp I am building.





    They are currently sealed, but I want to explore porting them (they don't make much bass at the moment). Internal dimensions are 7.5"x8.5"x13.5". The gear is:

    CSS RT1 ribbon (6 ohms)
    http://www.creativesound.ca/pdf/CSS-RT1-data-030508.pdf

    Tang-Band W4-1320SJF x2 (8 ohms each)
    https://www.parts-express.com/tang-b...eaker--264-915

    I was thinking of using a 3rd order xover @ 2500hz, but open to other ideas. I have a big bag of crossover parts, so I am definitely open to experimenting. I haven't done any enclosure modeling yet; last time I did was with WinISD many many years ago. What's the best tool to use now? They will be used in a smaller office in nearfield, no sub (for now). They don't need to be bass powerhouses, but a little kick would be nice. Any thoughts are greatly appreciated, thanks in advance!

  • #2
    WinISD is fine.

    Looks like the cabs are 0.5 cf each. W/a 2"id x 2" long port, a pair of those W4s should take 20w down into the 60s (should be plenty low to match up w/a future? sub). Most likely a full octave lower than they're running sealed. If the boxes are stuffed, you'd remove that and line the walls w/convoluted foam. Plug up the amp hole and put the vent behind the tweeter? 2.5k should work. Nothing wrong w/3k either.

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    • #3
      Thanks Chris, I really appreciate it. I believe they are already lined with convoluted foam, so that part is easy.

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      • #4
        Anyone know , under what condition the ribbons were measured in ? They look decent. Sorry not trying to hijack thread
        Attached Files

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        • #5
          Originally posted by nicholas_23 View Post
          Anyone know , under what condition the ribbons were measured in ? They look decent. Sorry not trying to hijack thread

          No worries, Id be curious to know as well, I believe they are based on the Aurum Cantus APR2.1. All of my other speakers have Aurum Cantus ribbons and sound amazing. These seem severely limited by the plate amps, which is another factor for replacing them.

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          • #6
            Try this for starters:

            3rd order HP: 2ohm series resistor and 6uF cap, 0.25mH shunt coil (to gnd. - a #20 is FINE), 18uF series cap. Negative polarity is indicated.
            2nd order LP: 0.80mH series coil (.4 ohm DCR in model), 8uF shunt cap.
            Fc just under 3k. About +4dBSC, about 90dB +/-1dB over ribbon's range.
            In YOUR 0.5cf box. 2"id x 2" port tunes to 70Hz w/an F3 under 60.

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            • #7
              Originally posted by Chris Roemer View Post
              Try this for starters:

              3rd order HP: 2ohm series resistor and 6uF cap, 0.25mH shunt coil (to gnd. - a #20 is FINE), 18uF series cap. Negative polarity is indicated.
              2nd order LP: 0.80mH series coil (.4 ohm DCR in model), 8uF shunt cap.
              Fc just under 3k. About +4dBSC, about 90dB +/-1dB over ribbon's range.
              In YOUR 0.5cf box. 2"id x 2" port tunes to 70Hz w/an F3 under 60.

              Thank you! This is awesome, I really appreciate the guidance. Ill report back with my results

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